The thyroid is a small gland below the skin and muscles at the front of the neck, at the spot where a bow tie would rest.
It's brownish red, with left and right halves (called lobes) that look like a butterfly's wings. It weighs less than an ounce, but helps the body do many things, such as get energy from food, grow, and go through sexual development. In younger children, it is also important for brain development.
Hypothyroidism (or underactive thyroid) is when the thyroid gland doesn't make enough of some important hormones. This makes the body use up energy more slowly, and chemical activity (metabolism) in the cells slows down.
Hypothyroidism is a common condition, especially in adult women. But kids can have it too. Some children are born with it — this is called congenital hypothyroidism. Others develop it later, usually late in childhood or as teens. The most common cause of hypothyroidism in kids and teens is the autoimmune disease Hashimoto's thyroiditis.
A person with mild hypothyroidism may feel just fine. In fact, it might cause no symptoms at all.
But if thyroid hormone levels get too low, symptoms can become more obvious. These include:
Hashimoto's thyroiditis (hah-she-MOE-toes thy-roy-DYE-tiss) is an autoimmune disease. It causes most cases of hypothyroidism in kids and teens. Hashimoto's thyroiditis is also called chronic lymphocytic thyroiditis.
Hashimoto's thyroiditis is an ongoing condition in which the immune system attacks the thyroid. Some people continue to have normal thyroid function. But often, over time the thyroid isn't making enough thyroid hormone, causing hypothyroidism. The body responds by sending a message to the thyroid to work harder to make enough hormone.
This, and the swelling the immune system causes as it attacks the gland, can make the thyroid get bigger, leading to a goiter. The thyroid can keep changing size over months or years.
To diagnose hypothyroidism and Hashimoto's thyroiditis, doctors ask about a person's symptoms, do an exam, and order blood tests. The tests measure:
Doctors treat an underactive thyroid with daily thyroid hormone replacement pills. The medicine is the same T4 that the body is no longer making. These will bring the body's levels of thyroid hormone back to normal.
This treatment is fairly simple, but a person will have doctor visits several times a year for an exam, blood tests, and medicine changes as needed.
Reviewed by: Tal Grunwald, MD
Date Reviewed: Apr 2, 2021